I got this from Clevite:The 4th coating on on a trimetal bearing is for storage. called a flash plating.

FLASH PLATING - Most trimetal bearings use what is called a “flash plating”. This is an: extremely thin layer (approx. .000030’) applied all over to provide uniform appearance and protection from rust and oxidation in storage. The common flash platings are either an alloy of lead and tin ranging from 10 to 20% tin content or pure tin. Pure tin has a more whitish color while the lead-tin alloys are a medium gray color. Both have a satin finish.

This is what mousefink was talking about "sliding layer" earlier! I mentioned a slide coat as we called it many years ago! I guess its called "flash plating" now. The 4th plating on on a trimetal bearing is for storage.

Let me ask this. When your getting a block machined or just planning on rebuilding one do you have to have it line honed or does the block need checked for any other clearences. Just asking to see what you all will say compared to what my machinist said. Have a feeling Im gonna be p i s s e d. Think Im gonna need to go somewhere else.

Hey guys I started taking my 350 roller apart and wanted to get your alls opinion on these main bearings. Do they look normal for having 150,000 miles on them?? Why do they get copper colored??

Id say are normal for mileage. Warn past usabilitty but normal. Check to see you have adiqut oiling at start up. This is ususaly indicitave of loss of or low oil pressure at start up. Extensive cranking at start up will cause this type of wear.

I always had 60 psi at start up everytime and never had any start up problems. I dont know, now Im thinkin about just junkin this crank and just makin this a 377. Actually ill keep the crank for a later project cause it looks good. I cant see any wear. But do I need to have this block line honed. I dont think I do. I guess ill need to mic it to make sure. Anyone know where to get a good cheap mic??

I always had 60 psi at start up everytime and never had any start up problems. I dont know, now Im thinkin about just junkin this crank and just makin this a 377. Actually ill keep the crank for a later project cause it looks good. I cant see any wear. But do I need to have this block line honed. I dont think I do. I guess ill need to mic it to make sure. Anyone know where to get a good cheap mic??

You need to have it checked!!! Or if you have a machinists long straight edge and good feeler gauges you can get a good Idea if its straight or not at home. There may be nothing wrong with the block? we are all just making good guesses LOL! We cant tell you if you need a line bore or not from a computer!
Maybe all the worn inserts had real tight oil clearance and the better ones had max oil clearance putting them further away from the crank, or some debree was under a few during assembly, maybe the good ones had just a little more coating then the rest, maybe at one time just your good looking inserts were changed during an inspection in the past or if there was a problem and the others were left alone because they checked ok etc, etc!

Check the pawn shops for tools a lot of machinists retire or upgrade and you can find them there!

Let me ask this. When your getting a block machined or just planning on rebuilding one do you have to have it line honed or does the block need checked for any other clearences. Just asking to see what you all will say compared to what my machinist said. Have a feeling Im gonna be p i s s e d. Think Im gonna need to go somewhere else.

I would expect the machinist to bore, deck and square the block like you asked him to do. Then if you wanted the saddles checked, he should be able to say whether they're OK as-is, or if they need honing, or if they need bored first. But a lot depends on what you have instructed him to do.

This is probably better answered by a machinist, but I'll take a stab at it:

You get a line hone if the saddles are close but not perfect. It's done routinely by many machinists for high performance builds to assure a good foundation. There are MANY little nuances to this as far as how much material is removed from the caps, chamfering the bores, mounting an oil pump (or part of one) to the rear main cap, etc. So I don't want to make it sound like it's a total no-brainer to do.

You would only get a line bore (followed by honing) if the saddles were out more than a little. This requires good equipment and a good operator w/a good touch. It may be easier/cheaper to get another block to use if the one you have needed line bored.

As far as do you HAVE to hone it? Often no, you don't. If the block is only going to be used as a street engine w/a mild build, as long as the saddles are reasonably close you can use it as-is. Not an ideal situation, but everything you do adds to the cost and you have to draw the line somewhere, else you'll end up w/a production block that will cost nearly what an aftermarket block would cost.

I was just curious cause I took my 73 chevy 350 block (which is not the block I took the crank stated above out of) to the machine shop which was the first time I ever been there but herd alot of good things about it. Here is the deal. I called him up one day and told him I have 4 chevy blocks and 8 pairs of heads and two intakes that I want to do some trading for some block work. He said well bring up what u got and Ill look at it. I took it all up there and he said we can work something out. He asked what its for and what I want done to it. I said its a street/strip build. If it needs bored do it 30 over which he said it does. also I didnt have the main caps so he said he would give me some and line hone it. Also first thing he is gonna inspect it, magnaflux it for cracks. I told him I wanted him to square it up and deck the block. I think thats all I told him, cant remember it was over two months ago. Someone told me on my 355 engine build thread that he should of told me to have the pistons I was going to use with the block when I dropped it off. I asked hime that if he bored it over .030 could I just buy .030 pistons and use them he said yes. Also I said can I buy stock main bearings and not have to do any measurments. He said when Im done you can buy standard size everything except .030 pistons and install them with no problem. Someone said he is full of s h i t. So Im thinkin I traded parts for block work thats gonna have to be re checked after I get it What you guys think. Keep in mind guys and bare with me that this is my first performance build so I kinda went into it diving right into it asking more than knowing.

Thanks Guys...

ChevroletSS

Also guys I had one of the main bearings I took off the crank I been talking about that was not copper colored and its been sittin since last friday and I just checked it out and there was a puddle of oil sitting in the center of the bearing and where the puddle is the bearing turned copper. It was all silver colored before. So does oil cause the coating to wear off and turn copper???

I was just curious cause I took my 73 chevy 350 block (which is not the block I took the crank stated above out of) to the machine shop which was the first time I ever been there but herd alot of good things about it. Here is the deal. I called him up one day and told him I have 4 chevy blocks and 8 pairs of heads and two intakes that I want to do some trading for some block work. He said well bring up what u got and Ill look at it. I took it all up there and he said we can work something out. He asked what its for and what I want done to it. I said its a street/strip build. If it needs bored do it 30 over which he said it does. also I didnt have the main caps so he said he would give me some and line hone it. Also first thing he is gonna inspect it, magnaflux it for cracks. I told him I wanted him to square it up and deck the block. I think thats all I told him, cant remember it was over two months ago. Someone told me on my 355 engine build thread that he should of told me to have the pistons I was going to use with the block when I dropped it off. I asked hime that if he bored it over .030 could I just buy .030 pistons and use them he said yes. Also I said can I buy stock main bearings and not have to do any measurments. He said when Im done you can buy standard size everything except .030 pistons and install them with no problem. Someone said he is full of s h i t. So Im thinkin I traded parts for block work thats gonna have to be re checked after I get it What you guys think. Keep in mind guys and bare with me that this is my first performance build so I kinda went into it diving right into it asking more than knowing.

Thanks Guys...

ChevroletSS

Ask him if the work is guarnteed. If so you may have to trust him. I would like to say things are always perfect but alot of the time even F'ed up work will still run strong and last a while. But of course it could have lasted longer if the work is done right. At some point in every build you just have to slap it together. If not you will spend too much time trying to make everything perfect in a street motor its not worth the effort.

He asked what its for and what I want done to it. I said its a street/strip build. If it needs bored do it 30 over which he said it does. also I didnt have the main caps so he said he would give me some and line hone it. Also first thing he is gonna inspect it, magnaflux it for cracks. I told him I wanted him to square it up and deck the block. I think thats all I told him, cant remember it was over two months ago. Someone told me on my 355 engine build thread that he should of told me to have the pistons I was going to use with the block when I dropped it off. I asked hime that if he bored it over .030 could I just buy .030 pistons and use them he said yes.

The piston to bore clearance will need to be checked to be sure it's OK. He really should have had the pistons before doing the final hone, though. That said, you're prob. gonna be OK, as long as you buy the kind of pistons he honed it for- cast/hyper pistons are fitted closer than forged pistons.

Quote:

Also I said can I buy stock main bearings and not have to do any measurments. He said when Im done you can buy standard size everything except .030 pistons and install them with no problem.

Unless you are getting a new crank or a polished used crank, you cannot use standard bearings.

He might have meant that you can install the crank w/the right undersize bearings and it will fit. Or it might just be a polished crank. There will be a big difference in the cost of polishing as opposed to turning.

Quote:

Also guys I had one of the main bearings I took off the crank I been talking about that was not copper colored and its been sittin since last friday and I just checked it out and there was a puddle of oil sitting in the center of the bearing and where the puddle is the bearing turned copper. It was all silver colored before. So does oil cause the coating to wear off and turn copper???

No. If the oil was acidic enough it could dissolve the plating if it's zinc, tin, or something like that. But uncontaminated oil will not touch it.

My turn.

Out of the 4 blocks you traded him, there wasn't one that could be bored 0.030" over that had all the caps?

BTW, you will be awfully lucky to get by w/just a main hone if he's replacing all the caps.

This could go on forever.
I am responding as I see it.
The question to me was would I have the block line bored. My experiences.
Racing ? Yes to correct any alignment problems and eliminate friction.
Street.
Probibly not if indeed this engine has 150,000 miles. If block has this much wear on bearings it probibly has ridges in cylinder the size of the grand cannon. Id insytall new bearings, that fit crank whatever the undersize may be as long as crank is round and true and even.
Bore block for new pistons.
normal other replacement parts that would be worn out. CAm Timing chain, gears, Head rebuild.

The indecater to me to line hone block is if you spun a main bearing. Line hone would be mandentory on any bearing spin.

To this post, I would have no problem putting in new parts the sizes the machienest stated he did work for. The coviot is make sure his work is correct and sizes he states are correct.
cas in point had work domne on one of my 400SBCs and crank was stated as a 10-10 under.
He gave me bearings for a 10-10 crank, and I did not check.
After assembeling 3 Main caps (Torque could not spin crank. Checked and hasd 20-20 crank. So if the machine work is correctly sized, makes no difference if you put different parts in as long as sized for that motor.

Hey Im just saying what I said I wanted done before I took the stuff off my truck. I didnt have caps and he had a **** load so he gave me some and said he would line hone it. The blocks I had were all 305s and he wanted the blocks. If they were 350 or bigger I would of kept every one of them. Actually I did keep one 305 to replace my 350 in my truck. As far as the crank for the motor I was going with new everything. Were starting to get off track some. The block Cobalt327, Hcompton and myself were talking about in the last two posts is not the one I took the bearings out of. Also I would never reuse main bearings. The cylinder walls actually look like they were just redone. Its crazy to me how good this block looks. Well I did baby it when it was in the truck but still its beautiful. What do you mean by piston to bore clearence. Is that the gap inbetween the two. Im gonna go take some pics of my 94 chevy block

"What do you mean by piston to bore clearence. Is that the gap inbetween the two."
YES

Aluminum expands about 1.7 times the rate of cast iron so there has to be room for that expansion. Rather then me typing this I'll just add this attachment! Remember: Different manufacturers and piston types(forged, cast,ETC,ETC, have different recommended clearances ) dont just open a repair manual and think that's correct!!!! you should always have the pistons before the block gets bored..That way the machine shop can do the final hone to get the exact piston clearance you need.. Most pistons you measure the skirts with a micrometer 90deg from the pin, just below the oil rings.

Measure the cylinder bore and subtract to get the clearance.

The piston is larger at the bottom of the skirt and smaller at the compression rings to allow for expansion of the piston dome. Pistons are also "cam-ground" (egg shaped, not perfectly round) as well so measuring somewhere other than the piston mfgr's. recommendations will give you an inaccurate number.

My machinist could of told me that. At least Ill have a fresh block when I get it for free and Ill have to just pay to get the final hone. Thanks for that article jester. Thanks everyone for the help. Ill scratch the idea of doing the other engine myself. Ill save it for a big project

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